Morphological changes in wild and less wild rivers in South-East Europe Guido Zolezzi Department of Civil Environmental and Mechanical Engineering University of Trento – ITALY Tirana, October 18, 2019 Outline • Morpho-dynamics = morphological dynamics • Different timescales ➔ different processes • One or few flood events ➔ • Multi-decadal channel adjustments • Case studies (wild and less wild) • Erzeni, Vermosh, Vjosa rivers () • Lumbardhi Pejes (Kosovo) • Prut river (Romania/Moldova) • Tagliamento river (Italy • Multiple stressors ➔ morphological quality (WFD 2000/60) • What is a wild river? Trento Tagliamento Prut

Lumbardhi Vermosh Pejes

Erzeni

Vjosa Channel Incision and coastal erosion in the Erzeni river – Lalzi bay system (1984 – 2015)

Catchment area: 760 km2

River length: 109 km

Mean annual flow: 18 m3 s-1 Mean annual sediment load: 4 ∙ 106 t y-1 Channel Incision and coastal erosion in the Erzeni river – Lalzi bay system (1984 – 2015)

Catchment area: 760 km2

River length: 109 km

Mean annual flow: 18 m3 s-1 Mean annual sediment load: 4 ∙ 106 t y-1 Channel Incision and coastal erosion in the Erzeni river – Lalzi bay system (1984 – 2015)

Catchment area: 760 km2

River length: 109 km

Mean annual flow: 18 m3 s-1 Mean annual sediment load: 4 ∙ 106 t y-1 Lalzi Bay: Observations on coastal erosion 1984 - 2015

Deleo et al., 2017

Sediments fluvial transport: 2.76 x 10 3m / y

3 Eroded volume: 1.52 x 10 m / y

55 % of the total transport ?

Considering the portion of the beach that was 2015 background image already moving, sediment transport reduction in the Erzeni is about 20 % Morphodynamic modelling of coastline evolution in response to reduced fluvial sediment supply Simulated erosion of the Erzeni river delta

Sea wave reconstruction

Sediment distribution along Lalzi Bay

• Intensive field measurements (250 grain size sampling, interviews, topo surveys) • 37 years one-hourly wave dataset • Morphodynamic model for coastline evolution (Oneline model, Deleo et al., 2017) Incision/narrowing of the lower river (1995–2015)

• Little available data • Integrated approach: topo surveys, dendrochronology, interviews • Massive sediment mining from river beds • Tendency to riverbed incision (2m in 20 years) • Channel narrowing, encroachment of riparian vegetation in the former active channel > 50 yr 10–15 yr

Ropa River (Polonia) – Rinaldi et al., 2005 Morphological effects of sediment mining in rivers

• Upstream and downstream Propagation of riverbed incision “wave” • Reduced sediment supply to coasts ➔ alteration of coastline evolution • Ordinary floods disconnected from previously active channel bars, which turn into more stable vegetated landofrms Channel narrowing in the Lumbardhi i Pejës downstream the town of Peja (Kosovo) 1968 – 2007

Paderno M., 2017, unpub MSc thesis, UniTrento Morphological quality of the Upper river basin (Kosovo, 2018) Paderno M., 2017, unpub MSc thesis, UniTrento • Heavily affected by sediment mining • MQI, Rinaldi et al 2016 – WFD implementation (Italy – REFORM EU project • 72 reaches, 192 river km Location of Vermosh river Reported increase in floods and debris flow but no data to assess «climate change» effects Aggradation in the Vermosh river related to heavy deforestation in the catchment

• Increased flood and intense sediment transport occurring in association with uncontrolled deforestation ➔ increase of flood flashiness (higher peak streamflow for the same rainfall) ➔ increase in soil erosion, sediment production and sediment transport to downstream areas Albanian rivers: contrasting styles of channel adjustments? Opposite river trajectories in relation to dominant stressor in the catchment? Upper part of catchments ➔ deforestation, little mining ➔ increased sediment supply ➔ aggradation ➔ increased flood risk Lower parts of catchments ➔ mining prevalent ➔ reduced sediment supply ➔ incision and coastal erosion Effects of incision Effects of aggradation (no visible banks …) The meandering Prut river at the border between Romania and Moldova

• One of the last long (>300km), partially «free» 2) meandering rivers in Europe 3) • Reservoir building in 1970s 1) 3) • Analysis of • Historical maps (1915, 1960, 1980) • Recent ortophoto (2015)

4)

Bisht T., 2019, unpub PhD thesis Reduced migration and narrowing of the meandering Prut river following dam construction

(A) (B) r-r s-s

s-r

r-s

f-a (D) (C) a-f

f-f a-a

Bisht T., 2019, unpub PhD thesis 1 2 3 4 River sections

Channel adjustments in Albanian rivers 1968 - 2015

+ 10 Landsat images (1975 – 2015) Data sources

Spada, D, 2016, unpub MSc thesis Regional reduction in mean channel widths 1968 – 2015 («trajectories»)

Automated extraction of morphological parameters (width, river length, sinuosity, …

Relative error of classification: < 5% Seman river

Molinari, P, 2017, unpub MSc thesis Also wild rivers follow trajectories: narrowing of Vjosa 1975 – 2015(unconfined reaches) Geomorphological trajectories 1968 – 2015: controlling factors?

Decreasing runoff trends 1958 – 1990 ➔ less effective floods? But morphological quality (Vjosa) is very high ➔ so what is a WILD river?

Laghetto G, 2019, unpub MSc thesis Vjosa river – recent eco-morphodynamics from Sentinel 2 satellite images Vjosa river: 2015 – 2018 reach-scale high degree of morphodynamics ➔ «wild» ?! Both duration and peak flood values are important to preserve dynamicity

Laghetto G, 2019, unpub MSc thesis Wild (large, braided) rivers: Tagliamento River (Alps) and Vjosa river (Balkans)

Welber et al, 2012 ESPL Tagliamento vs. Vjosa Different climate, biogeography and flow regime

Bertoldi et al, 2009 RRA Tagliamento also followed trajectories, but established as a «reference system», because it retains «reference processes» or «wild eco-morphodynamic processes» Map of river network Future of wild rivers? with planned reservoirs Modelling sediment transport at the catchment scale • CASCADE model (Schmitt et al., 2016)

Reaches with predicted reduction in sediment transport Predicted effect of hydropower development at the catchment scale

Predicted reaches with channel adjustments Reservoirs for which because of reduced sediment transport 80% of volume is predicted to be filled due to planned dams (orange) in less than 50 years

Stefani V, 2019, unpub MSc thesis Synthesis «Wild» rivers (Albania) • Highly dynamic river systems • Short distance from mountains to sea • High gradient ➔ high energy • Large sediment transport (gravel and fines) • Accelerated human stressors on rivers • Water abstractions • Sediment abstractions • Changes in land use (ex. Forrest cutting) • Hydropower These «wild» rivers can react very rapidly to anthropic changes (hydropower, sediment mining, etc…) ➔coastal dynamics ➔Reduced safety of structures and of human activities ➔Completely altered ecosystem dynamics Some take home messages

• «Wild rivers» rivers that retain «wild» processes • High scientific value: allow understanding and predicting river response to global changes • They catalize research interests ➔ relevant knowledge and datasets are rapidly developed • Several rivers in Albania and in the Balkan area have already been subject to strong hydro-morphological alteration • Sediment mining and land-use changes as multiple stressors together with hydropower • Morphodynamic modelling integrated with remote sensing and field observations offer great opportunities to support river management in conditions of data scarcity • Eco-morphodynamic trajectories and • Capacity building: interdisciplinary river scientists and manager Universities and THANKS !! research centers

Marco Bezzi Walter Bertoldi Marco Toffolon

Klodian Skrame Giovanni Besio Alfonso Vitti Christiane Zarfl Simone Bizzi Projects

Giacomo Laghetto Michele Paderno Livia Serrao Daniele Spada Vittoria Stefani Partners - NGOs Tania Floqi Martin Pusch Marco Tangi Paolo Molinari Tarun Bisht Francesca Benci Bestar Cekrezi Francesco Deleo